Diesel fuel



Patented May 6, 1952 DIESEL FUEL James B. Hlnkamp, Detroit, and Roy Sugimoto,

Royal Oak, Mich., assignors to Ethyl Corporation, New York. N. Y., a corporation of Delaware No Drawing. Application July 28, 1950, Serial No. 176,542

8 Claims.

This invention relates to a new composition of matter comprising a diesel fuel, a hydrocarbon fuel used in compression ignition engines, and an additive for improving its ignition properties. One of the fundamental advantages of the early form of the diesel engine was its ability to satisfactorily burn almost any type of liquid fuel. However, the intensive development which has led to the modern high-speed diesel engine has narrowed the range of suitable fuels to such a degree that present day fuels must meet many specifications. One of the most important specifications is ignition quality or the ease with which the fuel is ignited after it is injected into the cylinders of a diesel engine. This quality is measured in terms 01' octane number which is defined as the percentage of n-cetane in a n-cetane-a-methylnaphthalene blend which has an ignition quality comparable to the fuel in question. The use of fuels of poor quality results in starting dimculty and detonation, knocking, or rough running. The latter results in (1) increasing engine maintenance, (2) reduced engine life, and (3) excessive vibration and noise. Straight-run distillates from paraffln-base crude oils are generally of high ignition quality. Cracked distillates, or distillates from aromatic crudes are of inferior quality. Although most refiners have been and are able to supply adequate volumes of straight-run distillate or blends of straight-run with cracked distillate having a satisfactory ignition quality to meet the demand for diesel fuel, it is becoming increasingly difficult for them to do so. Furthermore, the rapidly expanding market for such fuels indicates that it will not be possible to continue to supply future demands without recourse to radically different refining techniques or the use of fuel additives.

The use of fuel additives to improve ignition quality (1) is more economical than the use of refining techniques, .(2) permits refinery operation for low pour point and other desirable qualities, and (3) permits the use of more dense, higher heat content stocks than could otherwise be utilized due to their low ignition quality. The use of such less expensive stock's permits greater economy of operation by decreasing both fuel cost and fuel consumption. However, expensive additives will not accomplish these results.

While the use of certain additives enhances the ignition properties of a fuel, an increase in cetane number at any great cost, does not justify the use of such additives. Besides the ability to improve the cetane number of a fuel, an additive should be stable and have good blending properties with the fuel.

It isan object of this invention to provide an additive which improves the ignition properties of diesel fuels at a moderate cost, which is stable and which blends readily with diesel distillates.

We have found that the use of nitramines accomplishes the above objects. Both monoalkyl and dialkylnitramines are effective with the dialkylnitramines being preferred. Among the nitramines of our invention are diethylnitramine. diisopropylnitramine, dimethylnitramine, methyl-n-propylnitramine, methylisopropylnitramine,

di-n-butylnitramine, diisobutylnitramine, diisoamylnitramine, methylnitramine, ethylnitramine. isopropylnitramine, n-butylnitramine, isoamylnitramine, cyclohexylnitramine, trimethylenedinitramine, and hexamethylenedinitramine.

In general the nitramines can be made by the dehydration of the corresponding alkyl ammonium nitrate salt. They can also be made by the direct nitration of'an alkyl amine with nitric acid. To illustrate specifically diethyIm'tr-amine was made in the following manner: 68 parts of diethylammonium nitrate, 3.15 parts of 100 per cent nitric acid, 5.44 parts of zinc chloride and 255 parts of acetic anhydride were heated in a reaction vessel for two and one-half hours at 50-55 C. while stirring. The reaction mixture was poured into a large beaker containing one kilogram of ice, neutralized with soda ash and extracted with ether. The ether layer was dried over anhydrous sodiumsulfate and distilled at atmospheric pressure. The yield of diethylnitramine was 35 parts or per cent.

The effectiveness of our additives in improving the ignition quality of a diesel fuel is illustrated by comparing ignition qualities of a base distillate stock with three fuel blends comprising the distillate stock to which was added different proportions of diethylnitramine. The ignition quality of the base stock and the fuel blend was determinedby comparison with a standard reference fuel in a C. F. R. engine, using the ignition delay method. According to the method described in American Society for Testing Materials, volume 36, I, 418 (1936), the value so obtained is the cetane number.

To illustrate the cetane number improvement obtained by the use of our additives, the following examples are given: To three samples of a 33 cetane number, straight-run refined distillate from Gulf Coast Crude was added diethylnitramine in amounts of 0.25, 0.5 and 1.0 weight per cent and the cetane number improvement, measured as given above. was 3.2, 6.0, and 8.0. respectively. To a fourth sample of the base stock was added 0.25 per cent of diisopropylnitramine and the cetane number improvement 'was 4.6. Likewise when diisobutylnitramine, di-n-butylnitramine, di-n-propylnitramine, methylisopropylnitramine, n-butylnitramine. cyclohexylnitr-amine, or hexamethylenedinitramine are substituted for the above materials, similar results are obtained.

Among the base stocks which can be improved by our additives are straight-run, catalyticallycracked or thermally-cracked stocks or blends thereof; prepared from Gulf Coast, West Texas, California, or Mid-Continent crude oils.

The above examples are merely illustrative of our invention and other examples, within the following claims, will be apparent to one skilled in the art.

We claim:

1. An improved diesel fuel containing a minor proportion of a lower saturated aliphatic nitramine in an amount suflicient to decrease the ignition delay period of the fuel.

2. The composition of claim 1 in which the nitramine is a lower dialkyl nitramine.

4 3. The composition of claim 1- in which the nitramine is a lower alkyl nitramine.

4'. The composition of claim 1 in which the nitramine is diethyl nitramine.

5. The composition of claim 1 in which the nitramine is diisopropyl nitramine.

6. The composition of claim 1 in which the nitramine is dimethyl nitramine.

7. The composition of claim 1 in which the nitramine is methyl nitramine.

8. The composition of claim 1 in which the nitramine is ethyl nitramine.

JAMES B. HINKAMP. ROY SUGIMOTO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,009,818 Salzberg et a1 July 30, 1935 2,527,292 Bahner Oct. 24, 1950 

1. AN IMPROVED DIESEL FUEL CONTAINING A MINOR PROPORTION OF A LOWER SATURATED ALIPHATIC NITRAMINE IN AN AMOUNT SUFFICIENT TO DECREASE THE IGNITION DELAY PERIOD OF THE FUEL. 